This invention relates to a method and system for purification of water, and more particularly to a method and structure for Purification of water to be fed to the roots to plants grown in greenhouse structures
Traditional greenhouse structures, consisting of transparent panes of glass forming a roof to enclose a growing area and having a heater for winter months, While adequate for many purposes, possess many shortcomings which make them unsuitable for year-round production of many types of fruits and vegetables in certain climatic conditions, e.g. in far Northern or far Southern climates Where temperature and light conditions may be poor. For example, outside air, which may contain substances which are not conducive to proper growth of plants, is permitted to enter. Also, exhaust products from the greenhouse heater which often is a natural gas or oil furnace, may be present in the environment within such greenhouses again causing reduced plant growth. The water Which is used in such greenhouses is often local water and again may contain impurities or compositions which impede plant growth. There is an increasing awareness of the detrimental impact of impurities in the air or water on plant growth. In addition, the concentration of elements required for plant growth such as calcium, nitrogen and phosphorus in water being fed to plants in conventional greenhouses may change from day-to-day, resulting in irregular plant growth.
As a result, in recent years there has been a trend towards development of controlled environment horticultural or agricultural installations. For example, Canadian Patent No. 1,097,075 of Miller issued Mar. 10, 1981 describes and illustrates a nutrient supply system for such a controlled environment agricultural installation incorporating nutrient film techniques in which plant root masses are arranged to be wetted by contact with a small stream of liquid nutrient. Capillary attraction or wicking then is relied upon to extend the nutrient-wetted area over and through the entire root mass. Nutrient supply is achieved by positioning the plant roots in long troughs and flowing a thin stream of liquid nutrient along the bottom to the trough permitting the stream to contact each of the plant root masses as it flows along. Excess nutrient is recycled usually after any needed replenishment of its compositional elements.
Such attempts to control in a greenhouse the various conditions responsible for plant growth have heretofore been extremely limited in scope. Thus for example in Miller Canadian Patent No. 1,097,075, only the nutrient feed is controlled. In Canadian Patent No. 982,426 of Delano et al issued Jan. 27, 1976, a method of controlling the amount of solar heat and light which enters a glass or plastic greenhouse is described wherein a liquid is coated on the glass or plastic film of the greenhouse. The liquid dries into a coating which is transparent under certain conditions and non-transparent under other conditions In Canadian Patent No. 955,748 of Glatti et al issued Oct. 8, 1984, the light passing through a translucent covering of a greenhouse is partially controlled by coating the inner surface of the translucent covering with a surface-active agent, which surface-active agent reduces the contact angle of water-condensate droplets formed on the inner surface thereof to below 75.degree..
Other patents of general background interest describing different types of greenhouse structures include U.S. Pat. No. 4,195,441 of Baldwin issued Apr. 1, 1980 (solar greenhouse in which plants are used as solar collectors to absorb solar radiation and store it in a heat reservoir beneath the greenhouse) and U.S. Pat. No. 4,352,256 of Kranz issued Oct. 5, 1982 (greenhouse structure including a central hub and arms comprising growth chambers extending radially outwardly therefrom).
None of these previous attempts to provide controlled environment greenhouses have adequately addressed the problems created by water of varying chemical content which is normally supplied to the plants in the greenhouse. Different plants require chemical nutrients of certain types for proper plant growth, these nutrients varying from plant to plant and even varying, for a given plant, at different stages of its growth. Water supplied to greenhouses may vary in chemical composition from season to season, whether that water comes from a well, municipal water source, river or lake, or elsewhere. It may contain some ingredients which are helpful to plant growth and others which are harmful to plant growth. In most greenhouse installations, minimal or no chemical analysis of the composition of water being fed to the plants is carried out, because of the added expense and marginal benefit to be achieved from such chemical analysis. Little or nothing could be done practically speaking in most cases to modify the composition of the water supplied to plants to remove any harmful ingredients from such water and complement the proper ingredients (which might be present in only trace amounts) contained therein with additional nutrient ingredients. Thus, it is usually assumed that the water being fed to greenhouse plants is pure. Nutrients and the like are then added to the water or to the soil about the plants in amounts deemed appropriate based on that assumption.
Also, with the increasing pollution of water supplies in most parts of the world, oftentimes by compounds or compositions which are harmful to plant growth, the results of impure water are increasingly being seen in reduced or less-than-desirable growth of horticultural crops in many regions.
Another problem with conventional greenhouse structures lies in the tremendous quantities of water needed to operate them. This problem is particularly significant in arid regions. Water is absorbed by the plants through their roots in such greenhouses and thereby lost into the plant and its produce. It is also lost to the environment in the greenhouse through transpiration from the plant leaves and through evaporation within the greenhouse.
It is an object of the present invention to provide a method and system for providing water of high purity to plants in a greenhouse which water is devoid of ingredients which may be deleterious to the growth of the plants. It is a further object of the present invention to provide a method and system of supplying water to the plants in a greenhouse which is extremely economical in water consumption when compared to traditional greenhouse methods and structures.